1. Field of the Invention
The present invention relates to a method, and a node and a network, for screening out unfamiliar messages and parameters.
2. Background Information
A telecommunication network includes gateway nodes which have the task of communicating with other surrounding networks. In a gateway node there is a need to be able to check which information is conveyed between different networks via the gateway node. This can include, for example, traffic conveyed by ISUP (Integrated Services User Part). ISUP is extremely information rich and exists in a couple of different versions. Furthermore, each version has a number of different national and operator-specific variants. This means there is a large risk that unfamiliar messages or parameters will come to a gateway node from a surrounding network.
There is a possibility in ISUP for the transmitter of a message to set a compatibility parameter. The parameter controls what a node shall do with a message or a parameter which it does not recognize. This means, however, that a long distance operator loses control over which messages and parameters he can convey in his network, because he must rely on those who send messages to set the parameters in a correct manner.
For a long distance operator it is especially important to solve this problem. In order to have a check on which services the operator wants to convey between two networks, the operator must recognize all the messages and parameters which arrive at the gateway nodes. A contributory reason for wanting to recognize all messages is, for example, to be able to track and document for accounting and debit purposes a customer's use of the long distance operator's network. If any of the long distance operator's customers chooses to update his network in order to institute new services then the long distance operator must follow along. Upgrading software in a telecommunication network is a slow process which means that the long distance operator will irremediably fall behind. But not even through upgrading can the long distance operator be certain to identify and debit for every message and parameter, because the operator's customers can use a variation of the protocol which is not known or available to the long distance operator.
From U.S. Pat. No. 5,062,108 it is known for a system to have stored data in order to identify and process messages. The system determines if a message uses a different number of identifiers. If this is the case, then the message is converted to a recognizable form.
ISUP also handles unfamiliar messages and parameters. This is done by reading and interpreting a compatibility parameter which is sent with the message. If there is no compatibility parameter sent with the message, then a predetermined action is taken. For example, the unfamiliar message or parameter is forwarded. This predetermined action applies for all messages or parameters.
Screening of known messages is known.